Part 2: Brain Blood Supply – Clinical Correlations & Stroke Syndromes!

Now that you’ve explored the intricate anatomy of the brain’s blood supply — from the Circle of Willis to the branching cerebral arteries — it’s time to connect that knowledge to clinical practice. Understanding which regions are perfused by each artery allows you to localise neurological deficits with precision, especially in acute stroke presentations.

Each arterial territory corresponds to distinct functional areas of the brain, so when blood flow is disrupted, the resulting symptoms offer vital clues. Whether it’s a sudden onset of aphasia, hemianopia, or ataxia, recognising the vascular pattern behind these signs helps clinicians rapidly identify the affected region, initiate appropriate imaging, and guide timely intervention.

Let’s walk through the major cerebral arteries and examine how their territories shape the clinical picture in stroke and other vascular syndromes.

🗺️ Arterial Territories & Clinical Impact

Understanding cerebral arterial territories is essential for localising stroke lesions and interpreting neurological deficits. Each major artery supplies distinct brain regions, and occlusion leads to characteristic patterns of dysfunction. Here's a breakdown of the key territories and their clinical relevance:

🔹 Anterior Cerebral Artery (ACA):

🧠 Territory Supplied:

• Medial aspects of the frontal and parietal lobes

• Superior motor and sensory cortices (leg area)

• Corpus callosum

• Cingulate gyrus

⚠️ Stroke Presentation:

• Contralateral leg weakness and sensory loss (due to medial motor/sensory cortex involvement)

• Frontal lobe signs: apathy, personality changes, impaired judgment, and urinary incontinence

• Transcortical motor aphasia (if dominant hemisphere affected)

📚 Clinical Relevance:

ACA strokes may be under-recognised due to subtle behavioural changes or isolated lower limb deficits. Always assess executive function, motivation, and cognition, especially in patients with preserved speech and arm strength. Bilateral ACA infarcts (e.g., from an unpaired ACA) can cause profound abulia or akinetic mutism.

🔹 Middle Cerebral Artery (MCA):

🧠 Territory Supplied:

• Lateral frontal, parietal, and temporal lobes

• Primary motor and sensory cortices (face and arm areas)

• Broca’s and Wernicke’s areas (dominant hemisphere)

• Basal ganglia via lenticulostriate arteries

⚠️ Stroke Presentation:

• Contralateral face and arm weakness

• Aphasia (dominant hemisphere) or hemispatial neglect (non-dominant hemisphere)

• Gaze deviation toward the side of the lesion

• Sensory loss, hemianopia, and possible hemiplegia if internal capsule involved

📚 Clinical Relevance:

MCA strokes are the most common type of ischaemic stroke, often embolic in origin (e.g., atrial fibrillation). They produce dense neurological deficits and are a key target for thrombolysis and thrombectomy. Always assess language, attention, and visual fields thoroughly

🔹 Posterior Cerebral Artery (PCA):

🧠 Territory Supplied:

• Occipital lobe

• Inferior temporal lobe

• Thalamus (posterior limb)

• Midbrain

⚠️ Stroke Presentation:

• Contralateral homonymous hemianopia (occipital cortex)

• Visual agnosia or alexia without agraphia (dominant hemisphere)

• Memory impairment (temporal lobe involvement)

• Thalamic syndrome: sensory loss, pain, and dysesthesia

📚 Clinical Relevance:

PCA strokes may present with isolated visual symptoms, which can be mistaken for ophthalmological issues. Always check for visual field deficits and neglect, especially in patients with preserved motor function. Thalamic involvement can cause complex sensory syndromes that evolve over time.

🔹 Vertebrobasilar System:

🧠 Territory Supplied:

• Brainstem (medulla, pons, midbrain)

• Cerebellum

• Thalamus

• Occipital cortex (via PCA branches)

⚠️ Stroke Presentation:

• Cranial nerve palsies (e.g., diplopia, dysarthria, dysphagia)

• Ataxia, vertigo, nausea

• Crossed findings: ipsilateral cranial nerve deficits with contralateral motor/sensory loss

• Locked-in syndrome (basilar artery occlusion): quadriplegia with preserved consciousness and vertical eye movement

📚 Clinical Relevance:

Posterior circulation strokes can be subtle or catastrophic. They often lack FAST signs and may be misdiagnosed as peripheral vertigo or migraine. Basilar artery occlusion is a neurological emergency — prompt recognition and imaging are critical.

⚠️ Key Clinical Syndromes

• Ischaemic stroke: MCA infarcts are the most common; emboli often originate from the left atrium in AF.
• Haemorrhagic stroke: Subarachnoid haemorrhage often stems from berry aneurysm rupture (e.g., at the anterior communicating artery).
• Watershed infarcts: Occur in low-flow states between ACA-MCA and MCA-PCA territories.
• Clinical Relevance: Watershed infarcts can mimic bilateral cortical symptoms in hypotensive patients—often presenting with "man-in-a-barrel" syndrome (arm/leg weakness sparing the face).

❓ Clinical Case Quiz: Can You Localise the Stroke?

A 72-year-old patient presents with:

Right arm and face weakness

Difficulty understanding speech

No visual field deficits

Which artery is most likely affected?

A) ACA

B) MCA

C) PCA

D) Basilar artery

💡 Drop your answers below!

Which hemisphere, which lobe, and what vascular territory do these symptoms point to?

💬 Comments

What clinical neuro cases have you found the most challenging so far? 👇

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